draft-ietf-mmusic-sdp-miscellaneous-caps-04.txt   draft-ietf-mmusic-sdp-miscellaneous-caps-05.txt 
MMUSIC WG M. Garcia-Martin MMUSIC WG M. Garcia-Martin
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track S. Veikkolainen Intended status: Standards Track S. Veikkolainen
Expires: September 14, 2013 Nokia Expires: November 04, 2013 Nokia
R. Gilman R. Gilman
March 13, 2013 May 03, 2013
Miscellaneous Capabilities Negotiation in the Session Description Miscellaneous Capabilities Negotiation in the Session Description
Protocol (SDP) Protocol (SDP)
draft-ietf-mmusic-sdp-miscellaneous-caps-04 draft-ietf-mmusic-sdp-miscellaneous-caps-05
Abstract Abstract
SDP has been extended with a capability negotiation mechanism SDP has been extended with a capability negotiation mechanism
framework that allows the endpoints to negotiate transport protocols framework that allows the endpoints to negotiate transport protocols
and attributes. This framework has been extended with a media and attributes. This framework has been extended with a media
capabilities negotiation mechanism that allows endpoints to negotiate capabilities negotiation mechanism that allows endpoints to negotiate
additional media-related capabilities. This negotiation is embedded additional media-related capabilities. This negotiation is embedded
into the widely-used SDP offer/answer procedures. into the widely-used SDP offer/answer procedures.
This memo extends the SDP capability negotiation framework to allow This memo extends the SDP capability negotiation framework to allow
endpoints to negotiate three additional SDP capabilities. In endpoints to negotiate three additional SDP capabilities. In
particular, this memo provides a mechanism to negotiate bandwidth particular, this memo provides a mechanism to negotiate bandwidth
('b=' line), connection data ('c=' line), and titles ('i=' line for ('b=' line), connection data ('c=' line), and titles ('i=' line for
each session or media). each session or media).
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 14, 2013. This Internet-Draft will expire on November 04, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Protocol Description . . . . . . . . . . . . . . . . . . . . . 3 3. Protocol Description . . . . . . . . . . . . . . . . . . . . 3
3.1. Extensions to SDP . . . . . . . . . . . . . . . . . . . . 4 3.1. Extensions to SDP . . . . . . . . . . . . . . . . . . . . 3
3.1.1. Bandwidth Capability . . . . . . . . . . . . . . . . . 6 3.1.1. Bandwidth Capability . . . . . . . . . . . . . . . . 6
3.1.2. Connection Data Capability . . . . . . . . . . . . . . 8 3.1.2. Connection Data Capability . . . . . . . . . . . . . 8
3.1.3. Title Capability . . . . . . . . . . . . . . . . . . . 12 3.1.3. Title Capability . . . . . . . . . . . . . . . . . . 12
3.2. Session Level versus Media Level . . . . . . . . . . . . . 15 3.2. Session Level versus Media Level . . . . . . . . . . . . 15
3.3. Offer/Answer model extensions . . . . . . . . . . . . . . 16 3.3. Offer/Answer model extensions . . . . . . . . . . . . . . 15
3.3.1. Generating the Initial Offer . . . . . . . . . . . . . 16 3.3.1. Generating the Initial Offer . . . . . . . . . . . . 16
3.3.2. Generating the Answer . . . . . . . . . . . . . . . . 16 3.3.2. Generating the Answer . . . . . . . . . . . . . . . . 16
3.3.3. Offerer Processing of the Answer . . . . . . . . . . . 17 3.3.3. Offerer Processing of the Answer . . . . . . . . . . 16
3.3.4. Modifying the Session . . . . . . . . . . . . . . . . 17 3.3.4. Modifying the Session . . . . . . . . . . . . . . . . 17
4. Field Replacement Rules . . . . . . . . . . . . . . . . . . . 17 4. Field Replacement Rules . . . . . . . . . . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17 5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6.1. New SDP Attributes . . . . . . . . . . . . . . . . . . . . 18 6.1. New SDP Attributes . . . . . . . . . . . . . . . . . . . 18
6.2. New Option Tags . . . . . . . . . . . . . . . . . . . . . 19 6.2. New Option Tags . . . . . . . . . . . . . . . . . . . . . 18
6.3. New SDP Capability Negotiation Configuration Parameters . 19 6.3. New SDP Capability Negotiation Configuration Parameters 19
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1. Normative References . . . . . . . . . . . . . . . . . . . 19 8.1. Normative References . . . . . . . . . . . . . . . . . . 19
8.2. Informative References . . . . . . . . . . . . . . . . . . 20 8.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
The Session Description Protocol (SDP) [RFC4566] is intended for The Session Description Protocol (SDP) [RFC4566] is intended for
describing multimedia sessions for the purposes of session describing multimedia sessions for the purposes of session
announcement, session invitation, and other forms of multimedia announcement, session invitation, and other forms of multimedia
session initiation. SDP has been extended with a capability session initiation. SDP has been extended with a capability
negotiation mechanism framework [RFC5939] which allows the endpoints negotiation mechanism framework [RFC5939] which allows the endpoints
to negotiate capabilities, such as support for Real-time Transport to negotiate capabilities, such as support for Real-time Transport
Protocol (RTP) [RFC3550] and Secure Real-time Transport Protocol Protocol (RTP) [RFC3550] and Secure Real-time Transport Protocol
(SRTP) [RFC3711]. The SDP media capabilities (SRTP) [RFC3711]. The SDP media capabilities
[I-D.ietf-mmusic-sdp-media-capabilities] provides negotiation [I-D.ietf-mmusic-sdp-media-capabilities] provides negotiation
capabilities to media lines as well. capabilities to media lines as well.
skipping to change at page 3, line 18 skipping to change at page 3, line 15
describing multimedia sessions for the purposes of session describing multimedia sessions for the purposes of session
announcement, session invitation, and other forms of multimedia announcement, session invitation, and other forms of multimedia
session initiation. SDP has been extended with a capability session initiation. SDP has been extended with a capability
negotiation mechanism framework [RFC5939] which allows the endpoints negotiation mechanism framework [RFC5939] which allows the endpoints
to negotiate capabilities, such as support for Real-time Transport to negotiate capabilities, such as support for Real-time Transport
Protocol (RTP) [RFC3550] and Secure Real-time Transport Protocol Protocol (RTP) [RFC3550] and Secure Real-time Transport Protocol
(SRTP) [RFC3711]. The SDP media capabilities (SRTP) [RFC3711]. The SDP media capabilities
[I-D.ietf-mmusic-sdp-media-capabilities] provides negotiation [I-D.ietf-mmusic-sdp-media-capabilities] provides negotiation
capabilities to media lines as well. capabilities to media lines as well.
The capability negotiation is embedded into the widely used SDP The capability negotiation is embedded into the widely used SDP offer
offer/answer procedure [RFC3264]. This memo provides the means to /answer procedure [RFC3264]. This memo provides the means to
negotiate further capabilities than those specified in the SDP negotiate further capabilities than those specified in the SDP
capability negotiation mechanism framework [RFC5939] and the SDP capability negotiation mechanism framework [RFC5939] and the SDP
media capabilities negotiation media capabilities negotiation
[I-D.ietf-mmusic-sdp-media-capabilities]. In particular, this memo [I-D.ietf-mmusic-sdp-media-capabilities]. In particular, this memo
provides a mechanism to negotiate bandwidth ('b='), connection data provides a mechanism to negotiate bandwidth ('b='), connection data
('c='), and session or media titles ('i='). ('c='), and session or media titles ('i=').
Since the three added capabilities are independent, it is not Since the three added capabilities are independent, it is not
expected that implementations will necessarily support all of them at expected that implementations will necessarily support all of them at
the same time. Instead, it is expected that applications will choose the same time. Instead, it is expected that applications will choose
skipping to change at page 4, line 4 skipping to change at page 3, line 44
2. Conventions Used in This Document 2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119 document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119] and indicate requirement levels for compliant [RFC2119] and indicate requirement levels for compliant
implementations. implementations.
3. Protocol Description 3. Protocol Description
3.1. Extensions to SDP
3.1. Extensions to SDP
The SDP Capability Negotiation Framework [RFC5939] and the SDP media The SDP Capability Negotiation Framework [RFC5939] and the SDP media
capabilities negotiation [I-D.ietf-mmusic-sdp-media-capabilities] capabilities negotiation [I-D.ietf-mmusic-sdp-media-capabilities]
specify attributes for negotiating SDP capabilities. These documents specify attributes for negotiating SDP capabilities. These documents
specify new attributes (e.g., 'acap', 'tcap', 'rmcap', 'omcap') for specify new attributes (e.g., 'acap', 'tcap', 'rmcap', 'omcap') for
achieving their purpose. In this document we define three new achieving their purpose. In this document we define three new
additional capability attributes for SDP lines of the general form: additional capability attributes for SDP lines of the general form:
type=value type=value
for types 'b', 'c', and 'i'. The corresponding capability attributes for types 'b', 'c', and 'i'. The corresponding capability attributes
skipping to change at page 4, line 27 skipping to change at page 4, line 25
o 'bcap': bandwidth capability o 'bcap': bandwidth capability
o 'ccap': connection data capability o 'ccap': connection data capability
o 'icap': title capability o 'icap': title capability
From the sub-rules of attribute ('a=') line in SDP [RFC4566], SDP From the sub-rules of attribute ('a=') line in SDP [RFC4566], SDP
attributes are of the form: attributes are of the form:
attribute = (att-field ":" att-value) / att-field attribute = (att-field ":" att-value) / att-field
att-field = token att-field = token
att-value = byte-string att-value = byte-string
Capability attributes use only the 'att-field:att-value' form. Capability attributes use only the 'att-field:att-value' form.
The new capabilities may be referenced in potential configurations The new capabilities may be referenced in potential configurations
('a=pcfg') or in latent configurations ('a=lcfg'), as productions ('a=pcfg') or in latent configurations ('a=lcfg'), as productions
conforming to the <extension-config-list> as respectively defined in conforming to the <extension-config-list> as respectively defined in
RFC 5939 [RFC5939] and the SDP media capabilities specification RFC 5939 [RFC5939] and the SDP media capabilities specification
[I-D.ietf-mmusic-sdp-media-capabilities]. [I-D.ietf-mmusic-sdp-media-capabilities].
extension-config-list = ["+"] ext-cap-name "=" ext-cap-list extension-config-list = ["+"] ext-cap-name "=" ext-cap-list
ext-cap-name = 1*(ALPHA / DIGIT) ext-cap-name = 1*(ALPHA / DIGIT)
; ALPHA and DIGIT defined in RFC 5234 ; ALPHA and DIGIT defined in RFC 5234
ext-cap-list = 1*VCHAR ; VCHAR defined in RFC 5234 ext-cap-list = 1*VCHAR ; VCHAR defined in RFC 5234
The optional "+" is used to indicate that the extension is mandatory The optional "+" is used to indicate that the extension is mandatory
and MUST be supported in order to use that particular configuration. and MUST be supported in order to use that particular configuration.
The new capabilities may also be referenced in actual configurations The new capabilities may also be referenced in actual configurations
('a=acfg') as productions conforming to the <sel-extension-config> ('a=acfg') as productions conforming to the <sel-extension-config>
defined in RFC 5939 [RFC5939]. defined in RFC 5939 [RFC5939].
sel-extension-config = ext-cap-name "=" 1*VCHAR sel-extension-config = ext-cap-name "=" 1*VCHAR
The specific parameters are defined in the individual description of The specific parameters are defined in the individual description of
each capability, below. each capability, below.
The 'bcap', 'ccap', and 'icap' capability attributes can be provided The 'bcap', 'ccap', and 'icap' capability attributes can be provided
at the SDP session and/or media level. According to the SDP at the SDP session and/or media level. According to the SDP
Capability Negotiation [RFC5939], each extension capability must Capability Negotiation [RFC5939], each extension capability must
specify the implication of making it part of a configuration at the specify the implication of making it part of a configuration at the
media level. media level.
skipping to change at page 5, line 26 skipping to change at page 5, line 28
'ccap', and 'icap' capability attributes, when declared at session 'ccap', and 'icap' capability attributes, when declared at session
level, are to be interpreted as-if that attribute was provided with level, are to be interpreted as-if that attribute was provided with
that value at the session level. The 'bcap', 'ccap' and 'icap' that value at the session level. The 'bcap', 'ccap' and 'icap'
capability attributes declared at media level, are to be interpreted capability attributes declared at media level, are to be interpreted
as-if that capability attribute was declared at the media level. as-if that capability attribute was declared at the media level.
For example, extending the example in For example, extending the example in
[I-D.ietf-mmusic-sdp-media-capabilities] with 'icap' and 'bcap' [I-D.ietf-mmusic-sdp-media-capabilities] with 'icap' and 'bcap'
capability attributes, we get the following SDP: capability attributes, we get the following SDP:
v=0 v=0
o=- 25678 753849 IN IP4 192.0.2.1 o=- 25678 753849 IN IP4 192.0.2.1
s= s=
c=IN IP4 192.0.2.1 c=IN IP4 192.0.2.1
t=0 0 t=0 0
a=bcap:1 CT:200 a=bcap:1 CT:200
a=icap:1 Video conference a=icap:1 Video conference
m=audio 54320 RTP/AVP 0 m=audio 54320 RTP/AVP 0
a=rmcap:1 L16/8000/1 a=rmcap:1 L16/8000/1
a=rmcap:2 L16/16000/2 a=rmcap:2 L16/16000/2
a=pcfg:1 m=1|2 pt=1:99,2:98 a=pcfg:1 m=1|2 pt=1:99,2:98
m=video 66544 RTP/AVP 100 m=video 66544 RTP/AVP 100
a=rmcap:3 H263-1998/90000 a=rmcap:3 H263-1998/90000
a=rtpmap:100 H264/90000 a=rtpmap:100 H264/90000
a=pcfg:10 m=3 pt=3:101 b=1 i=1 a=pcfg:10 m=3 pt=3:101 b=1 i=1
Figure 1: Example SDP offer with bcap and icap defined at session Figure 1: Example SDP offer with bcap and icap defined at session
level level
The above SDP defines one PCMU audio stream and one H.264 video The above SDP defines one PCMU audio stream and one H.264 video
stream. It also defines two RTP-based media capabilities ('rmcap' stream. It also defines two RTP-based media capabilities ('rmcap'
numbered 1 and 2), using L16 audio at 8 kbps and 16 kbps, numbered 1 and 2), using L16 audio at 8 kbps and 16 kbps,
respectively, as well as an RTP-based media capability for H.263 respectively, as well as an RTP-based media capability for H.263
video ('rmcap' numbered 3). The RTP-based media capabilities all video ('rmcap' numbered 3). The RTP-based media capabilities all
appear at the media level. The example also contains a single appear at the media level. The example also contains a single
skipping to change at page 6, line 39 skipping to change at page 6, line 42
where <bw-cap-num> is a unique integer within all the bandwidth where <bw-cap-num> is a unique integer within all the bandwidth
capabilities in the entire SDP, which is used to number the bandwidth capabilities in the entire SDP, which is used to number the bandwidth
capability, and can take a value between 1 and 2^31-1 (both capability, and can take a value between 1 and 2^31-1 (both
included). The other elements are as defined for the 'b=' field in included). The other elements are as defined for the 'b=' field in
SDP [RFC4566]. SDP [RFC4566].
This format satisfies the general attribute production rules in SDP This format satisfies the general attribute production rules in SDP
[RFC4566] according to the following Augmented Backus-Naur Form [RFC4566] according to the following Augmented Backus-Naur Form
(ABNF) [RFC5234] syntax: (ABNF) [RFC5234] syntax:
att-field =/ "bcap" att-field =/ "bcap"
att-value =/ bw-cap-num 1*WSP bwtype ":" bandwidth att-value =/ bw-cap-num 1*WSP bwtype ":" bandwidth
bw-cap-num = 1*10(DIGIT) ; DIGIT defined in RFC 5234 bw-cap-num = 1*10(DIGIT) ; DIGIT defined in RFC 5234
Figure 2: Syntax of the bcap attribute Figure 2: Syntax of the bcap attribute
Negotiation of bandwidth per media stream can be useful when Negotiation of bandwidth per media stream can be useful when
negotiating media encoding capabilities with different bandwidths. negotiating media encoding capabilities with different bandwidths.
3.1.1.1. Configuration Parameters 3.1.1.1. Configuration Parameters
The SDP capability negotiation framework [RFC5939] provides for the The SDP capability negotiation framework [RFC5939] provides for the
existence of the 'pcfg' and 'acfg' attributes. The concept is existence of the 'pcfg' and 'acfg' attributes. The concept is
skipping to change at page 7, line 46 skipping to change at page 7, line 51
need for such definitions is not seen, we have not restricted this, need for such definitions is not seen, we have not restricted this,
as it is not restricted in SDP [RFC4566] either. as it is not restricted in SDP [RFC4566] either.
The bandwidth parameter to the actual configuration attribute The bandwidth parameter to the actual configuration attribute
('a=acfg') is formulated as a <sel-extension-config> with ('a=acfg') is formulated as a <sel-extension-config> with
ext-cap-name = "b" ext-cap-name = "b"
hence hence
sel-extension-config =/ sel-bandwidth-config sel-extension-config =/ sel-bandwidth-config
sel-bandwidth-config = "b=" bw-cap-list ; bw-cap-list as above. sel-bandwidth-config = "b=" bw-cap-list ; bw-cap-list as above.
Figure 4: Syntax of the bandwidth parameter in 'acfg' attributes Figure 4: Syntax of the bandwidth parameter in 'acfg' attributes
3.1.1.2. Option tag 3.1.1.2. Option tag
The SDP Capability Negotiation Framework [RFC5939] allows for The SDP Capability Negotiation Framework [RFC5939] allows for
capability negotiation extensions to be defined. Associated with capability negotiation extensions to be defined. Associated with
each such extension is an option tag that identifies the extension in each such extension is an option tag that identifies the extension in
question. Hereby, we define a new option tag "bcap-v0" that question. Hereby, we define a new option tag "bcap-v0" that
identifies support for the bandwidth capability. The endpoints using identifies support for the bandwidth capability. The endpoints using
skipping to change at page 9, line 5 skipping to change at page 9, line 5
where <conn-cap-num> is a unique integer within all the connection where <conn-cap-num> is a unique integer within all the connection
capabilities in the entire SDP, which is used to identify the capabilities in the entire SDP, which is used to identify the
connection data capability, and can take a value between 1 and 2^31-1 connection data capability, and can take a value between 1 and 2^31-1
(both included). The other elements are as defined in [RFC4566]. (both included). The other elements are as defined in [RFC4566].
This format corresponds to the [RFC4566] attribute production rules This format corresponds to the [RFC4566] attribute production rules
according to the following Augmented Backus-Naur Form (ABNF) according to the following Augmented Backus-Naur Form (ABNF)
[RFC5234] syntax: [RFC5234] syntax:
att-field =/ "ccap" att-field =/ "ccap"
att-value =/ conn-cap-num 1*WSP nettype SP addrtype att-value =/ conn-cap-num 1*WSP nettype SP addrtype
SP connection-address SP connection-address
conn-cap-num = 1*10(DIGIT) ; 1 to 2^31-1, inclusive conn-cap-num = 1*10(DIGIT) ; 1 to 2^31-1, inclusive
; DIGIT defined in RFC 5234 ; DIGIT defined in RFC 5234
Figure 5: Syntax of the ccap attribute Figure 5: Syntax of the ccap attribute
The 'ccap' capability attribute allows for expressing alternative The 'ccap' capability attribute allows for expressing alternative
connection address ('c=') lines in SDP as part of the SDP capability connections address ("c=") lines in SDP as part of the SDP capability
negotiation process. The 'ccap' capability attribute is intended to negotiation process. One of the primary use cases for this is
be used only when there is no other mechanism available for offering alternative connection addresses where the <nettype> is "IN"
negotiating alternative connection address information, such as when or "PSTN", i.e. selecting between IP based bearer or a circuit-
the <nettype> is different among the alternative addresses (e.g. switched bearer.
"IN" and "PSTN"). The 'ccap' attribute MUST NOT be used in
situations where an existing mechanism (such as Interactive By supporting the "IN" <nettype>, the 'ccap' attribute enables the
Connectivity Establishment (ICE) [RFC5245]) can be used to select signaling of multiple IPv4 and IPv6 addresses, however the Standards
between different connection addresses (e.g. "IP4" and "IP6" or Track mechanism for negotiation of alternative IP addresses in SDP is
different IP addresses within the same IP address family). Interactive Connectivity Establishment (ICE) [RFC5245]. The 'ccap'
attribute does not change that and hence the combined set of actual
and potential configurations (as defined in [RFC5939]) for any given
media description MUST NOT use the 'ccap' attribute to negotiate more
than one address with an IN network type (i.e., it is not permissible
to select between "IP4" and "IP6" address families or different IP
addresses within the same IP address family.
Figure 6 is an example of an SDP offer that includes a 'ccap' Figure 6 is an example of an SDP offer that includes a 'ccap'
capability attribute. An audio stream can be setup with an RTP flow capability attribute. An audio stream can be setup with an RTP flow
or establishing a circuit-switched audio stream: or establishing a circuit-switched audio stream:
v=0 v=0
o=2987933123 2987933123 IN IP4 198.51.100.7 o=2987933123 2987933123 IN IP4 198.51.100.7
s=- s=-
t=0 0 t=0 0
a=creq:med-v0,ccap-v0 a=creq:med-v0,ccap-v0
m=audio 38902 RTP/AVP 0 8 m=audio 38902 RTP/AVP 0 8
c=IN IP4 198.51.100.7 c=IN IP4 198.51.100.7
a=ccap:1 PSTN E164 +15555556666 a=ccap:1 PSTN E164 +15555556666
a=tcap:2 PSTN a=tcap:2 PSTN
a=omcap:1 - a=omcap:1 -
a=acap:1 setup:actpass a=acap:1 setup:actpass
a=acap:2 connection:new a=acap:2 connection:new
a=acap:3 cs-correlation:callerid:+15555556666 a=acap:3 cs-correlation:callerid:+15555556666
a=pcfg:1 c=1 t=2 m=1 a=1,2,3 a=pcfg:1 c=1 t=2 m=1 a=1,2,3
Figure 6: Example SDP offer with a ccap attribute Figure 6: Example SDP offer with a ccap attribute
The example in Figure 6 represents an SDP offer indicating an audio The example in Figure 6 represents an SDP offer indicating an audio
flow using RTP, such as the one represented in Figure 7 or an audio flow using RTP, such as the one represented in Figure 7 or an audio
flow using a circuit-switched connection, such as the one represented flow using a circuit-switched connection, such as the one represented
in Figure 8. in Figure 8.
v=0 v=0
o=2987933123 2987933123 IN IP4 198.51.100.7 o=2987933123 2987933123 IN IP4 198.51.100.7
s=- s=-
t=0 0 t=0 0
m=audio 38902 RTP/AVP 0 8 m=audio 38902 RTP/AVP 0 8
c=IN IP4 198.51.100.7 c=IN IP4 198.51.100.7
Figure 7: Equivalent SDP offer with the RTP flow Figure 7: Equivalent SDP offer with the RTP flow
v=0 v=0
o=2987933123 2987933123 IN IP4 198.51.100.7 o=2987933123 2987933123 IN IP4 198.51.100.7
s=- s=-
t=0 0 t=0 0
m=audio 9 PSTN - m=audio 9 PSTN -
c=PSTN E164 +15555556666 c=PSTN E164 +15555556666
a=setup:actpass a=setup:actpass
a=connection:new a=connection:new
a=cs-correlation:callerid:+15555556666 a=cs-correlation:callerid:+15555556666
Figure 8: Equivalent SDP offer with the circuit-switched flow Figure 8: Equivalent SDP offer with the circuit-switched flow
This document does not define any mechanism for negotiating or This document does not define any mechanism for negotiating or
describing different port numbers and hence the port number from the describing different port numbers and hence the port number from the
"m=" line MUST be used by default. Exceptions to this default can be "m=" line MUST be used by default. Exceptions to this default can be
provided by extension mechanisms or network type specific rules. provided by extension mechanisms or network type specific rules.
This draft defines an exception when the network type is "PSTN", in This draft defines an exception when the network type is "PSTN", in
which case the port number is replaced with 9 (the "discard" port) as which case the port number is replaced with 9 (the "discard" port) as
described in Session Decription Protocol (SDP) Extension For Setting described in Session Decription Protocol (SDP) Extension For Setting
Up Audio and Video Media Streams over Circuit-Switched Bearers in the Up Audio and Video Media Streams over Circuit-Switched Bearers in the
Public Switched Telephone Network (PSTN) [I-D.ietf-mmusic-sdp-cs] Public Switched Telephone Network (PSTN) [I-D.ietf-mmusic-sdp-cs].
An endpoint offering alternative IP and PSTN bearers MUST include the
IP media description in the actual configuration (IP address in the
"c=" line and port number in the "m=" line), and the PSTN media
description in the potential configuration.
3.1.2.1. Configuration Parameters 3.1.2.1. Configuration Parameters
The SDP Capability Negotiation Framework [RFC5939] provides for the The SDP Capability Negotiation Framework [RFC5939] provides for the
existence of the 'pcfg' and 'acfg' attributes, which can convey one existence of the 'pcfg' and 'acfg' attributes, which can convey one
or more configurations to be negotiated. The concept is extended by or more configurations to be negotiated. The concept is extended by
the Media Capabilities Negotiation the Media Capabilities Negotiation
[I-D.ietf-mmusic-sdp-media-capabilities] with an 'lcfg' attribute [I-D.ietf-mmusic-sdp-media-capabilities] with an 'lcfg' attribute
that conveys latent configurations. that conveys latent configurations.
skipping to change at page 11, line 4 skipping to change at page 11, line 9
existence of the 'pcfg' and 'acfg' attributes, which can convey one existence of the 'pcfg' and 'acfg' attributes, which can convey one
or more configurations to be negotiated. The concept is extended by or more configurations to be negotiated. The concept is extended by
the Media Capabilities Negotiation the Media Capabilities Negotiation
[I-D.ietf-mmusic-sdp-media-capabilities] with an 'lcfg' attribute [I-D.ietf-mmusic-sdp-media-capabilities] with an 'lcfg' attribute
that conveys latent configurations. that conveys latent configurations.
In this document we define a <connection-config> parameter to be used In this document we define a <connection-config> parameter to be used
to specify a connection data capability in a potential or latent to specify a connection data capability in a potential or latent
configuration attribute. The parameter follows the form of an configuration attribute. The parameter follows the form of an
<extension-config-list>, with <extension-config-list>, with
ext-cap-name = "c" ext-cap-name = "c"
ext-cap-list = conn-cap-list ext-cap-list = conn-cap-list
where, according to the following Augmented Backus-Naur Form (ABNF) where, according to the following Augmented Backus-Naur Form (ABNF)
[RFC5234] syntax: [RFC5234] syntax:
extension-config-list =/ conn-config-list extension-config-list =/ conn-config-list
conn-config-list = ["+"] "c=" conn-cap-list conn-config-list = ["+"] "c=" conn-cap-list
conn-cap-list = conn-cap-num *(BAR conn-cap-num) conn-cap-list = conn-cap-num *(BAR conn-cap-num)
conn-cap-num = 1*10(DIGIT) ; 1 to 2^32-1 inclusive conn-cap-num = 1*10(DIGIT) ; 1 to 2^32-1 inclusive
Figure 9: Syntax of the connection data parameter in 'lcfg' and Figure 9: Syntax of the connection data parameter in 'lcfg' and
'pcfg' attributes 'pcfg' attributes
Each capability configuration alternative contains a single Each capability configuration alternative contains a single
connection data capability attribute number and refers to the conn- connection data capability attribute number and refers to the conn-
cap-num capability number defined explicitly earlier in this cap-num capability number defined explicitly earlier in this
document, and hence MUST be between 1 and 2^31-1 (both included). document, and hence MUST be between 1 and 2^31-1 (both included).
The connection data capability allows the expression of only a single The connection data capability allows the expression of only a single
capability in each alternative, rather than a list of capabilities, capability in each alternative, rather than a list of capabilities,
skipping to change at page 11, line 42 skipping to change at page 11, line 48
this parameter prefixed with a plus sign and does not support this this parameter prefixed with a plus sign and does not support this
extension MUST treat that potential configuration as not valid. extension MUST treat that potential configuration as not valid.
The connection data parameter to the actual configuration attribute The connection data parameter to the actual configuration attribute
('a=acfg') is formulated as a <sel-extension-config> with ('a=acfg') is formulated as a <sel-extension-config> with
ext-cap-name = "c" ext-cap-name = "c"
hence hence
sel-extension-config =/ sel-connection-config sel-extension-config =/ sel-connection-config
sel-connection-config = "c=" conn-cap-num ; as defined above. sel-connection-config = "c=" conn-cap-num ; as defined above.
Figure 10: Syntax of the connection data parameter in 'acfg' Figure 10: Syntax of the connection data parameter in 'acfg'
attributes attributes
3.1.2.2. Option tag 3.1.2.2. Option tag
The SDP Capability Negotiation Framework [RFC5939] solution allows The SDP Capability Negotiation Framework [RFC5939] solution allows
for capability negotiation extensions to be defined. Associated with for capability negotiation extensions to be defined. Associated with
each such extension is an option tag that identifies the extension in each such extension is an option tag that identifies the extension in
question. Hereby, we define a new option tag of "ccap-v0" that question. Hereby, we define a new option tag of "ccap-v0" that
skipping to change at page 13, line 27 skipping to change at page 13, line 27
In this document we define a new capability attribute: the Title In this document we define a new capability attribute: the Title
capability 'icap'. This attribute lists session or media titles as capability 'icap'. This attribute lists session or media titles as
capabilities, according to the following definition: capabilities, according to the following definition:
"a=icap:" title-cap-num 1*WSP text "a=icap:" title-cap-num 1*WSP text
where <title-cap-num> is a unique integer within all the connection where <title-cap-num> is a unique integer within all the connection
capabilities in the entire SDP, which is used to identify the capabilities in the entire SDP, which is used to identify the
particular title capability, and can take a value between 1 and particular title capability, and can take a value between 1 and
2^31-1 (both included). <text> is a human-readable text that 2^31-1 (both included). <text> is a human-readable text that
indicates the purpose of the session or media stream it is supposed indicates the purpose of the session or media stream it is supposed
to characterize. to characterize.
As an example, one might use: As an example, one might use:
a=icap:1 Document Camera a=icap:1 Document Camera
to define a title capability number 1 to identify a particular source to define a title capability number 1 to identify a particular source
of a media stream. of a media stream.
The title capability attribute satisfies the general attribute The title capability attribute satisfies the general attribute
production rules in SDP [RFC4566] according to the following production rules in SDP [RFC4566] according to the following
Augmented Backus-Naur Form (ABNF) [RFC5234] syntax: Augmented Backus-Naur Form (ABNF) [RFC5234] syntax:
att-field =/ "icap" att-field =/ "icap"
att-value =/ title-cap-num 1*WSP text att-value =/ title-cap-num 1*WSP text
; text defined in RFC 4566 ; text defined in RFC 4566
title-cap-num = 1*10(DIGIT) ; DIGIT defined in RFC 5234 title-cap-num = 1*10(DIGIT) ; DIGIT defined in RFC 5234
Figure 11: Syntax of the icap attribute Figure 11: Syntax of the icap attribute
3.1.3.1. Configuration Parameters 3.1.3.1. Configuration Parameters
The SDP Capability Negotiation Framework [RFC5939] provides for the The SDP Capability Negotiation Framework [RFC5939] provides for the
existence of the 'pcfg' and 'acfg' attributes. The concept is existence of the 'pcfg' and 'acfg' attributes. The concept is
extended by the SDP media capabilities negotiation extended by the SDP media capabilities negotiation
[I-D.ietf-mmusic-sdp-media-capabilities] with an 'lcfg' attribute [I-D.ietf-mmusic-sdp-media-capabilities] with an 'lcfg' attribute
that conveys latent configurations. that conveys latent configurations.
In this document, we define a <title-config-list> parameter to be In this document, we define a <title-config-list> parameter to be
used to convey title capabilities in a potential or latent used to convey title capabilities in a potential or latent
configuration. This parameter is defined as an <extension-config- configuration. This parameter is defined as an <extension-config-
list> with the following associations: list> with the following associations:
skipping to change at page 14, line 25 skipping to change at page 14, line 22
configuration. This parameter is defined as an <extension-config- configuration. This parameter is defined as an <extension-config-
list> with the following associations: list> with the following associations:
ext-cap-name = "i" ext-cap-name = "i"
ext-cap-list = title-cap-list ext-cap-list = title-cap-list
This leads to the following definition for the title capability This leads to the following definition for the title capability
parameter: parameter:
extension-config-list =/ title-config-list extension-config-list =/ title-config-list
title-config-list = ["+"] "i=" title-cap-list title-config-list = ["+"] "i=" title-cap-list
title-cap-list = title-cap-num *(BAR title-cap-num) title-cap-list = title-cap-num *(BAR title-cap-num)
; BAR defined in RFC 5939 ; BAR defined in RFC 5939
title-cap-num = 1*10(DIGIT) ; DIGIT defined in RFC 5234 title-cap-num = 1*10(DIGIT) ; DIGIT defined in RFC 5234
Figure 12: Syntax of the title capability parameter in 'lcfg' and Figure 12: Syntax of the title capability parameter in 'lcfg' and
'pcfg' attributes 'pcfg' attributes
Each potential capability configuration contains a single title Each potential capability configuration contains a single title
capability attribute number where 'title-cap-num' is the title capability attribute number where 'title-cap-num' is the title
capability number defined explicitly earlier in this document, and capability number defined explicitly earlier in this document, and
hence must be between 1 and 2^31-1 (both included). The title hence must be between 1 and 2^31-1 (both included). The title
capability allows the expression of only a single capability in each capability allows the expression of only a single capability in each
alternative, since no more than a single title field is permitted per alternative, since no more than a single title field is permitted per
skipping to change at page 15, line 4 skipping to change at page 14, line 47
block. Nevertheless, it is still allowed to express alternative block. Nevertheless, it is still allowed to express alternative
potential title configurations separated by a vertical bar ("|"). potential title configurations separated by a vertical bar ("|").
An endpoint includes a plus sign ("+") in the configuration attribute An endpoint includes a plus sign ("+") in the configuration attribute
to mandate support for this extension. An endpoint that receives to mandate support for this extension. An endpoint that receives
this parameter prefixed with a plus sign and does not support this this parameter prefixed with a plus sign and does not support this
extension MUST treat that potential configuration as not valid. extension MUST treat that potential configuration as not valid.
The title parameter to the actual configuration attribute ('a=acfg') The title parameter to the actual configuration attribute ('a=acfg')
is formulated as a <sel-extension-config> with is formulated as a <sel-extension-config> with
ext-cap-name = "i" ext-cap-name = "i"
hence hence
sel-extension-config =/ sel-title-config
sel-extension-config =/ sel-title-config sel-title-config = "i=" title-cap-num ; as defined above.
sel-title-config = "i=" title-cap-num ; as defined above.
Figure 13: Syntax of the title parameter in 'acfg' attributes Figure 13: Syntax of the title parameter in 'acfg' attributes
3.1.3.2. Option Tag 3.1.3.2. Option Tag
At present, it is difficult to envision a scenario in which the At present, it is difficult to envision a scenario in which the
'icap' attribute must be supported or the offer must be rejected. In 'icap' attribute must be supported or the offer must be rejected. In
most cases, if the icap attribute or its contents were to be ignored, most cases, if the icap attribute or its contents were to be ignored,
an offered configuration could still be chosen based on other an offered configuration could still be chosen based on other
criteria such as configuration numbering. However, one might imagine criteria such as configuration numbering. However, one might imagine
skipping to change at page 16, line 48 skipping to change at page 16, line 45
When the answering party receives the offer, and if it supports the When the answering party receives the offer, and if it supports the
required capability negotiation extensions, it SHOULD select the most required capability negotiation extensions, it SHOULD select the most
preferred configuration it can support for each media stream, and preferred configuration it can support for each media stream, and
build the answer accordingly, as defined in Section 3.6.2 of the SDP build the answer accordingly, as defined in Section 3.6.2 of the SDP
Capability Negotiation [RFC5939]. Capability Negotiation [RFC5939].
If the connection data capability is used in a selected potential If the connection data capability is used in a selected potential
configuration chosen by the answerer, that offer configuration MUST configuration chosen by the answerer, that offer configuration MUST
by default use the port number from the actual offer configuration by default use the port number from the actual offer configuration
(i.e. the "m=" line), unless the network type is "PSTN", in which (i.e. the "m=" line), unless the network type is "PSTN", in which
case the default port MUST be assumed to be 9. Extensions may be case the default port MUST be assumed to be 9. Extensions may be
defined to negotiate the port number explicitly instead. defined to negotiate the port number explicitly instead.
3.3.3. Offerer Processing of the Answer 3.3.3. Offerer Processing of the Answer
When the offerer receives the answer, it MUST process the media lines When the offerer receives the answer, it MUST process the media lines
according to normal SDP processing rules to identify the media according to normal SDP processing rules to identify the media
stream(s) accepted by the answer, if any, as defined in Section 3.6.3 stream(s) accepted by the answer, if any, as defined in Section 3.6.3
of the SDP Capability Negotiation [RFC5939]. The 'acfg' attribute, of the SDP Capability Negotiation [RFC5939]. The 'acfg' attribute,
if present, MUST be used to verify the proposed configuration used to if present, MUST be used to verify the proposed configuration used to
form the answer, and to infer the lack of acceptability of higher- form the answer, and to infer the lack of acceptability of higher-
preference configurations that were not chosen. preference configurations that were not chosen.
3.3.4. Modifying the Session 3.3.4. Modifying the Session
skipping to change at page 17, line 18 skipping to change at page 17, line 15
according to normal SDP processing rules to identify the media according to normal SDP processing rules to identify the media
stream(s) accepted by the answer, if any, as defined in Section 3.6.3 stream(s) accepted by the answer, if any, as defined in Section 3.6.3
of the SDP Capability Negotiation [RFC5939]. The 'acfg' attribute, of the SDP Capability Negotiation [RFC5939]. The 'acfg' attribute,
if present, MUST be used to verify the proposed configuration used to if present, MUST be used to verify the proposed configuration used to
form the answer, and to infer the lack of acceptability of higher- form the answer, and to infer the lack of acceptability of higher-
preference configurations that were not chosen. preference configurations that were not chosen.
3.3.4. Modifying the Session 3.3.4. Modifying the Session
If, at a later time, one of the parties wishes to modify the If, at a later time, one of the parties wishes to modify the
operating parameters of a session, e.g. by adding a new media stream, operating parameters of a session, e.g. by adding a new media
or by changing the properties used on an existing stream, it may do stream, or by changing the properties used on an existing stream, it
so via the mechanisms defined for SDP offer/answer [RFC3264] and in may do so via the mechanisms defined for SDP offer/answer [RFC3264]
accordance with the procedures defined in Section 3.6.4 of the SDP and in accordance with the procedures defined in Section 3.6.4 of the
Capability Negotiation [RFC5939]. SDP Capability Negotiation [RFC5939].
4. Field Replacement Rules 4. Field Replacement Rules
To simplify the construction of SDP records, given the need to To simplify the construction of SDP records, given the need to
include fields within the media description in question for endpoints include fields within the media description in question for endpoints
that do not support capabilities negotiation, we define some simple that do not support capabilities negotiation, we define some simple
field-replacement rules for those fields invoked by potential or field-replacement rules for those fields invoked by potential or
latent configurations. In particular, any 'i=' or 'c=' line invoked latent configurations. In particular, any 'i=' or 'c=' line invoked
by a configuration MUST replace the corresponding line, if present by a configuration MUST replace the corresponding line, if present
within the media description in question. Any 'b=' line invoked by a within the media description in question. Any 'b=' line invoked by a
skipping to change at page 18, line 18 skipping to change at page 18, line 14
6. IANA Considerations 6. IANA Considerations
6.1. New SDP Attributes 6.1. New SDP Attributes
IANA is hereby requested to register new attributes in the "att-field IANA is hereby requested to register new attributes in the "att-field
(both session and media level)" of the "Session Description Protocol (both session and media level)" of the "Session Description Protocol
(SDP) Parameters" registry, according to the following registration (SDP) Parameters" registry, according to the following registration
form: form:
Attribute name: bcap Attribute name: bcap
Long form name: Bandwidth Capability Long form name: Bandwidth Capability
Type of attribute: Both media and session level Type of attribute: Both media and session level
Subject to charset: No Subject to charset: No
Purpose: Negotiate session or media-level bandwidths Purpose: Negotiate session or media-level bandwidths
Appropriate values: See RFC XXXX Section 3.1.1 Appropriate values: See RFC XXXX Section 3.1.1
[Note to the RFC Editor: Please replace the above RFC XXXX [Note to the RFC Editor: Please replace the above RFC XXXX
with the RFC number of this specification. with the RFC number of this specification.
Contact name: Miguel A. Garcia, Contact name: Miguel A. Garcia,
Miguel.A.Garcia@ericsson.com Miguel.A.Garcia@ericsson.com
Attribute name: ccap Attribute name: ccap
Long form name: Connection Data Capability Long form name: Connection Data Capability
Type of attribute: Both media and session level Type of attribute: Both media and session level
Subject to charset: No Subject to charset: No
Purpose: Negotiate media-level connection data Purpose: Negotiate media-level connection data
Appropriate values: See RFC XXXX Section 3.1.2 Appropriate values: See RFC XXXX Section 3.1.2
[Note to the RFC Editor: Please replace the above RFC XXXX [Note to the RFC Editor: Please replace the above RFC XXXX
with the RFC number of this specification. with the RFC number of this specification.
Contact name: Miguel A. Garcia, Contact name: Miguel A. Garcia,
Miguel.A.Garcia@ericsson.com Miguel.A.Garcia@ericsson.com
Attribute name: icap Attribute name: icap
Long form name: Title Capability Long form name: Title Capability
Type of attribute: Both media and session level Type of attribute: Both media and session level
Subject to charset: Yes Subject to charset: Yes
Purpose: Negotiate human-readable information Purpose: Negotiate human-readable information
describing the session or media describing the session or media
Appropriate values: See RFC XXXX Section 3.1.3 Appropriate values: See RFC XXXX Section 3.1.3
[Note to the RFC Editor: Please replace the above RFC XXXX [Note to the RFC Editor: Please replace the above RFC XXXX
with the RFC number of this specification. with the RFC number of this specification.
Contact name: Miguel A. Garcia, Contact name: Miguel A. Garcia,
Miguel.A.Garcia@ericsson.com Miguel.A.Garcia@ericsson.com
6.2. New Option Tags 6.2. New Option Tags
IANA is hereby requested to add the new option tags "bcap-v0", IANA is hereby requested to add the new option tags "bcap-v0",
"ccap-v0", and "icap-v0", defined herein, to the "SDP Capability "ccap-v0", and "icap-v0", defined herein, to the "SDP Capability
Negotiation Option Tag subregistry" of the "Session Description Negotiation Option Tag subregistry" of the "Session Description
Protocol (SDP) Parameters" registry. Protocol (SDP) Parameters" registry.
6.3. New SDP Capability Negotiation Configuration Parameters 6.3. New SDP Capability Negotiation Configuration Parameters
IANA is hereby requested to add the new parameter identifiers "b" for IANA is hereby requested to add the new parameter identifiers "b" for
"bandwidth", "c" for "connection data", and "i" for "title" to the "bandwidth", "c" for "connection data", and "i" for "title" to the
"SDP Capability Negotiation Configuration Parameters" subregistry of "SDP Capability Negotiation Configuration Parameters" subregistry of
skipping to change at page 19, line 42 skipping to change at page 19, line 38
[I-D.ietf-mmusic-sdp-media-capabilities] [I-D.ietf-mmusic-sdp-media-capabilities]
Gilman, R., Even, R., and F. Andreasen, "Session Gilman, R., Even, R., and F. Andreasen, "Session
Description Protocol (SDP) Media Capabilities Description Protocol (SDP) Media Capabilities
Negotiation", draft-ietf-mmusic-sdp-media-capabilities-17 Negotiation", draft-ietf-mmusic-sdp-media-capabilities-17
(work in progress), January 2013. (work in progress), January 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, with Session Description Protocol (SDP)", RFC 3264, June
June 2002. 2002.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5939] Andreasen, F., "Session Description Protocol (SDP) [RFC5939] Andreasen, F., "Session Description Protocol (SDP)
Capability Negotiation", RFC 5939, September 2010. Capability Negotiation", RFC 5939, September 2010.
8.2. Informative References 8.2. Informative References
[I-D.ietf-mmusic-sdp-cs] [I-D.ietf-mmusic-sdp-cs]
Garcia, M. and S. Veikkolainen, "Session Description Garcia, M. and S. Veikkolainen, "Session Description
Protocol (SDP) Extension For Setting Up Audio and Video Protocol (SDP) Extension For Setting Up Audio and Video
Media Streams Over Circuit-Switched Bearers In The Public Media Streams Over Circuit-Switched Bearers In The Public
Switched Telephone Network (PSTN)", Switched Telephone Network (PSTN)", draft-ietf-mmusic-sdp-
draft-ietf-mmusic-sdp-cs-17 (work in progress), cs-18 (work in progress), April 2013.
January 2013.
[RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
Session Description Protocol (SDP) for ATM Bearer Session Description Protocol (SDP) for ATM Bearer
Connections", RFC 3108, May 2001. Connections", RFC 3108, May 2001.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, July 2003.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004. RFC 3711, March 2004.
[RFC4574] Levin, O. and G. Camarillo, "The Session Description [RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574, August 2006. Protocol (SDP) Label Attribute", RFC 4574, August 2006.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, Traversal for Offer/Answer Protocols", RFC 5245, April
April 2010. 2010.
Authors' Addresses Authors' Addresses
Miguel A. Garcia-Martin Miguel A. Garcia-Martin
Ericsson Ericsson
Calle Via de los Poblados 13 Calle Via de los Poblados 13
Madrid, 28033 Madrid 28033
Spain Spain
Phone: +34 91 339 1000 Phone: +34 91 339 1000
Email: miguel.a.garcia@ericsson.com Email: miguel.a.garcia@ericsson.com
Simo Veikkolainen Simo Veikkolainen
Nokia Nokia
P.O. Box 226 P.O. Box 226
NOKIA GROUP, FI 00045 NOKIA GROUP, FI 00045
Finland Finland
Phone: +358 50 486 4463 Phone: +358 50 486 4463
Email: simo.veikkolainen@nokia.com Email: simo.veikkolainen@nokia.com
Robert R. Gilman Robert R. Gilman
3243 W. 11th Ave. Dr. 3243 W. 11th Ave. Dr.
Broomfield, Colorado 80020 Broomfield, Colorado 80020
U.S.A. U.S.A.
Phone: +1 303 898 9780 Phone: +1 303 898 9780
Email: bob_gilman@comcast.net Email: bob_gilman@comcast.net
 End of changes. 47 change blocks. 
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